Maricopa County Sheriff Joe Arpaio is famous for chasing after undocumented immigrants in his Arizona jurisdiction.

But the man known as "America's Toughest Sheriff" hasn't been following the law, according to a decision issued by a federal judge on Friday.

The judge found that the Maricopa County Sheriff's Office (MCSO) has systematically employed racial profiling against Hispanics. The office was ordered to stop using Hispanic ancestry as a factor in making law-enforcement decisions.

"The MCSO is disappointed by the outcome in this decision," said Tim Casey, a lawyer for the sheriff's office. "The MCSO's position is that it has never used race and will never use race in making its law-enforcement decisions."

Arpaio can appeal the decision, but Casey said that they would begin working internally to remedy any problems raised in the ruling.

"The sheriff respects the court and its authority and it will comply," Casey said.

The four-and-a-half-year case involved several plaintiffs, including two Latino siblings from Chicago who believed they had been subject to racial profiling, according to The Arizona Republic.

The parties were represented by the American Civil Liberties Union (ACLU) and pro-bono attorneys from a Bay-Area law firm.

Dan Pochoda, the legal director for the ACLU of Arizona, said this was a victory for community members in Maricopa who have spoken out against Arpaio over this exact issue.

"The sheriff's pronouncement that he's never been found to do anything wrong is going to have to go by the wayside," Pochoda said.

The practical implications are unclear -- it's possible the office may need to undergo monitoring for the use of racial profiling, or supply data to the court to authenticate its practices, but not certain. The parties are scheduled to reconvene on June 14 to discuss implementation of the decision.

The ruling is a long-awaited victory for immigrant-rights activists who have criticized Arpaio's tactics for years. The judge's ruling explicitly points out that Arpaio overstepped the line when trying to enforce immigration laws.

"The evidence introduced at trial establishes that, in the past, the MCSO has aggressively protected its right to engage in immigration and immigration-related enforcement operations even when it had no accurate legal basis for doing so," U.S. District Judge Murray Snow wrote.